The invention concerns a fixture with a member that can be moved into different operating positions by means of a control shaft, and having an attachment flange through whose front face is led to the outside one end of the control shaft for connection to a driving contrivance that is to be attached to the front face of the attachment flange.
These types of fixtures are known. In the case of these fixtures, the attachment flange forms, with its front face, an interface for the driving contrivance. Of course, the driving contrivance is to be mounted on the front face of the attachment flange. Since the control shaft is to be led to the outside with its one end through the front face of the attachment flange, the driving contrivance is constructed such that it is brought into active engagement with the control shaft when it is placed on the front face of the attachment flange. For this purpose, the driving contrivance generally has an output shaft driven by a drive, said output shaft capable of being coupled to the control shaft of the fixture, and actually in axially-aligning fashion when the control shaft of the fixture is driven in rotary fashion by the output shaft of the driving contrivance. The dimensions of the precedingly-described interface between the fixture and the driving contrivance to be attached thereto are standardized.
Falling under the precedingly-described fixture, for example, is also a control valve for controlling the flow of a medium, as for example a liquid. The movable member here serves for closing the control valve. In general, the movable element in a control valve is constructed as a shutter-disk, ball, stopcock or cone, and is joined in rotation-fast manner at its hinge and/or rotation point with the control shaft, the axis of which aligns with the hinge and/or axis of rotation, so that the control shaft must be correspondingly rotated for closing and opening the movable element.
In order to be able to detect and indicate the position of the control shaft and therewith the operating position of the movable member, it was necessary, up until now, to provide additional adapters and components which, in general, were mounted either between the fixture and the driving contrivance or at an auxiliary interface at the driving contrivance.
In the first case, i.e. when mounting between the fixture and the driving contrivance, placed on the front face of the attachment flange was a transmitter unit, while the driving contrivance was then attached on the side of the transmitter unit away from the front face of the attachment flange. Resulting from this was that the driving contrivance had to be disposed at some distance from the fixture. Then, in order that the active connection with the driving contrivance not be lost, a shaft-connecting piece had to be interposed inside the transmitter unit, between the free end of the control shaft and the driving contrivance. For an control valve of the above-described kind, a transmitter unit of this type displayed a frameform adapter that was mounted with its one side on the front face of the control valve, with the driving arrangement being set on its oppositely-lying side with its mating counter flange, along with the previously-described intervening shaft piece, which was passed through borings in the adapter and provided with an indicating pin. This indicating pin therewith provided a mechanical indication of the rotational position of the control shaft. Since, however, as a rule, the viewing conditions at the place where the control valve is installed are quite different from application to application, it was later necessary to calibrate the indicating pin. Showing up from this was that this later calibration was not always correctly carried out. Because of the frequently confined space conditions prevailing at the location of installation, even with correct calibration of the indicating pin, a trouble-free recognition of the rotational position of the control shaft was not always possible.
A significant disadvantage of this type of arrangement of the transmitter unit between the fixture and the driving contrivance lies in the increase of the structural volume of the entire arrangement made up of fixture and driving contrivance, which, of course, because of the frequently tight space conditions prevailing at the installation location, is not always possible and also contradicts the corresponding standard. For these reasons, a direct mounting of the driving contrivance on the front face of the attachment flange with the fixture is absolutely necessary.
In the second case, namely when mounting the transmitter unit at an auxiliary interface at the driving contrivance, indeed met is the requirement for a direct attachment of the driving contrivance to the fixture, however the total structural volume is not reduced by this since these types of transmitter units consisted of a box-shaped housing with end switches disposed therein. Because of the need to provide an auxiliary interface for the transmitter unit at the driving contrivance, expense was increased still more. Besides this, the position of the control shaft with this type of transmitter unit could only be indicated indirectly, which, particularly in the case of an error in the driving contrivance, led to an erroneous indication.
Finally, there existed another disadvantage of the previously-described transmitter units, in that they had to be installed as auxiliary components on the fixture and/or the driving contrivance, whereby the expense for mounting increased.